Permanent magnet blowout for a contactor



y 21, 1963 F. KRETZSCHMAR 3,090,854

PERMANENT MAGNET BLOWOUT FOR A CONTACTOR Filed NOV. 21, 1960 I5 Sheets-Sheet 1 I N VEN TOR. Fpg g c Kftl'ZS CIIMAQ May 21, 1963 zscH R 3,090,854

PERMANENT MAGNET BLOWOUT FOR A CONTACTOR Filed Nov. 21, 1960 3 Sheets-Sheet 2 INVENTOR.

fksose/ck KQHZSCHMA? a F. KRETZSCHMAR PERMANENT MAGNET BLOWOUT FOR A CONTACTOR Filed Nov. 21, 1960 May 21, 1963 3 Sheets-Sheet 3 INVENTOR. @EoqwcK A/FETZSCHMAQ M @w a United States Patent Gifl1 3,ti%,854 Patented May 21, 1963 3,090,854 PERMANENT MAGNET BLOWOUT FOR A CONTACTOR Frederick Kretzschmar, Nanuet, N.Y., assignor to Ward Leonard Electric Co., Mount Vernon, N.Y., a corporation of New York Filed Nov. 21, 1960, Ser. No. 70,508 6 Claims. (Cl. 200-147) This invention relates to blowout devices for quenching a spark formed on separation of two conducting electrical contacts.

It is well known that a circuit tends to maintain the current across two contacts as the contacts are separated to produce an are. This arcing causes the engaging surfaces of the contacts to become pitted, thereby reducing the amount of current the contacts are capable of passing without overheating and causing the surfaces to unevenly engage. Various means may be provided to prevent or stop this sparking and reduce its adverse affects. One method is to produce a magnetic field extending transverse to the relative movement of the contacts which quenches or extinguishes the are.

An object of this invention is to provide a spark quenching device that is small and easily mounted on a contactor or relay and has a magnetic field for quenching the are formed between separating electrical contacts.

Another object of this invention is to provide an arc quenching device comprising a few parts.

Other and further objects of the invention will be apparent from the following description taken in connection with drawings in which:

FIG. 1 is a perspective view of the single piece holding member supported by a bracket;

FIG. 2 is a sectional view taken along lines 22 of the embodiment of FIG. 1;

FIG. 3 is another sectional view taken along lines 3-3 of FIG. 2;

FIG. 4 is a top view of the single piece embodiment of FIG. 1;

FIG. 5 is a diagrammatic illustration of the relationship of the contacts to the permanent magnets and the magnetic field;

F G. 6 is a perspective view of the two piece holding member separated for purposes of illustration;

FIG. 7 is a perspective view of one of the pieces of the holding member of the second embodiment;

FIG. 8 is an end view of the assembled two piece embodiment supported by a bracket;

FIG. 9 is a sectional view taken along lines 9--9 of FIG. 8;

FIG. 10 is a top view of the two piece embodiment; and

FIG. 11 is a sectional view taken along lines 11-11 of FIG. 9.

Referring to the embodiment shown in FIGS. 14, the holding or supporting member 10 is a single piece of :molded plastic insulating material. The member is symmetrically formed on each side of the vertical plane parallel to the sides and on each side of the horizontal plane. The member 10' comprises spaced side portions 11 and 12 and an intermediate mounting portion 14 between the side portions and forming a cavity 13 therewith. A bracket 15 is attached to the mounting portion and supports the holding member 10 to position the ends of the fixed contact 17 and the moving contact 18 in the cavity 13 between the side portions 11 and 12.

The contact 17 comprises a contact button 26 attached in a fixed position to the stationary contact post assembly 16 of the relay by means of the threaded portion 17a and nut 17b. The contact 18 is of the resilient finger or bar type mounted on a movable armature of an electromagnet or otherwise suitably actuated. The contact buttons are located in the cavity 13 between the side portions and transfer the current from one contact to the other, and on separation of the contacts an arc may be formed between the contact buttons. The are quenching device may be used with other types of contacts and its use is not restricted to the form illustrated and described herein.

The side portions 11 and 12 have inner walls 20, 21 and the intermediate portion 14 has an inner end wall 22. The side walls and end wall define three sides of the cavity. There is an opening 23 at the top of the cavity and an opening 24 at the bottom. The ends of the side portions form an end opening 25 through which the movable contact 18 enters the cavity 13. The contact 17 enters the cavity through the lower opening 24.

As best illustrated in FIG. 5 the fixed contact 17 is positioned in the middle of the cavity with the contact button 26 adjacent the end wall 22. The movable contact 18 may be positioned above or below the fixed contact and moves in and out of engagement with the fixed contact through a stroke within the cavity 13.

As illustrated in FIG. 5 the pairs of contacts are in side by side relation. The side portions fit between the pairs of contacts. The side walls 2%, 21 and end wall 22 of each holding member form an arc barrier between the pairs of contacts.

The side portions have suificient thickness for forming recesses 30, 31 in which the magnets are located. The recesses 30, 31 are rectangular in shape and are defined by side walls 34 and end wall 35 in side portion 11 and side walls 36 and end wall 37 in side portion 12. The side walls are narrow to form a shallow recess. The magnets are rectangular and approximately the same size as the recesses. The end walls 35 and 37 have grooves 38, 39 adjacent the side walls forming the raised centers 40, 41. The magnets 32, 33 fit in the recesses and are securely fastened to the supporting member by means of an epoxy resin on the centers 40', 41. The grooves 38, 39 extending around the centers 4 41 provide space for the excess resin so that the resin does not flow to the outside surfaces. The outer surfaces of the magnets and the respective side portions are generally even.

The width and length of the magnets are slightly less than the width and length of the side portions so that the magnets horizontally overlap with the entire cavity 13. The permanent magnets may be of any permanently magnetizable material. However, to secure all the advantages of the invention it is preferred that the nonconducting ceramic type be used. Thus the magnets and holding member form a non-conducting body. The magnet 32 is formed with the north pole on the side surface 65 and the south pole on the other side surface 66, and magnet 33 is formed with the north pole on the side surface 66a and the south pole on the side surface 65a. Thus the inner or facing walls of the magnet are of opposite polarity and the line of magnetic force flow across the cavity 13 transverse or normal to the movement of the movable contact 18. The extensive overlap between the magnets and the cavity fills the cavity with lines of force normal to the side walls.

Thus as the movable contact button 27 disengages the fixed contact button 126 while current is being transferred, any are or spark formed will be generally normal to the lines of force and the arc is drawn up and out by the magnetic field. This drawing or stretching of the arc extinguishes it.

The contact buttons are positioned so that 30% or less of each magnet is adjacent to the contacts with the remaining portion of the magnets positioned away from the contacts in order to draw the are away from the contacts. As illustrated in FIGS. 4 and 9 the contact buttons are positioned off from the mid-point of the magnets. The end wall 22 is located adjacent the middle of the magnets. Thus in the mounting of the arc quenching device on a contactor or relay, the contact buttons are preferably off center.

The holding member 19 is positioned by the bracket 15 fastened to the intermediate portion 14. The intermediate portion is formed with identical notches 4-2, 4 3 spaced by a web 44. The web 44 forms a supporting means to fasten the holding member 10 in two positions to a bracket. The notches have side walls 45, 45a, 46, 46a and end walls 47, respectiveiy. Since the magnets are identical and are identically positioned by the side portions except for the polarity of the sides, the bracket may be attached to the holding member either in notch 42 or 43, depending on the desired relation of the polarity of magnets.

The bracket 15 has a generally L-shaped end 49 attached to the holding member and an L-shaped end 49a attached to the stationary contact post assembly 16. The end 49:: is fastened by a bolt 67 and has a raised portion 63 fitting in a notch 6% in the frame 16 to position the bracket vertically. The L-shaped end 49' fits snugly into either notch 42, 43 engaging the side walls 45, 45a or 46, 46a to prevent rotation or movement of the supporting member. The web 44 has a hole 60 and a bolt 61 passes through the hole and threads into the bracket 15 to securely and fixedly fasten the number 1.0 to the frame 16.

Another embodiment is illustrated in FIGS. 6-11 in which the holding member is formed in two separable and identical pieces 59, 50a. The piece is rotated 180 to interleave with the piece 5% and form a unitary holding member symmetrical about horizontal and vertical planes in the same manner as the holding member of the single piece embodiment. There are differences between the single piece embodiment and the two piece embodiment. The holding member 143:: has side portions 51, 51a with recesses '79, 76a for the permanent magnets 32, 33. The recesses 79, 76a have side walls 74, 74a and end walls 75, 75a respectively. The end walls 75 and 75a have grooves 78, 78a for receiving the epoxy resin securing the magnets in place. The recesses 76, 70a are identical to recesses 36, 31 and the magnets are more or less even with the outer side surfaces.

The cavity 53 is formed by the assembled pieces 50, 59a and the fixed and movable contacts are positioned in the same manner as in the embodiment of FIG. 1. The intermediate portions form overlapping fastening members 55, 55a extending from one side portion to the other. The facing surfaces 81, 81a are flat and in firm contact as illustrated in FlGS. 8 and 9. Barriers 82, 82a extend along the end adjacent to the cavity 53 to separate the cavity from the bracket 15 fastened to the intermediate portions. At the other end raised portions 83, 85a extend between the side portions to recess the exterior surfaces 84, 84a of the intermediate portions. The two pieces are laterally and longitudinally interlocked so that where the two pieces are fitted together no relative movement can occur between the two pieces except the separating movement away from one another. Blocks 85, 85a are formed as part of a respective side portion and extend inwardly and are spaced from the intermediate portion attached to the same side portion. The intermediate portions of the respective pieces fit into either space 86 or 86a to interlock the two pieces. The barriers 82, 82:: also overlap with the blocks 85, 85a. The raised portions 83, 830 also extend to the side portion of the other piece and are provided with steps 87, 87a to permit the overlapping of identical pieces. The surface 88 engages the step 87a and the surface 88a engages the step 87. Thus the two pieces are interlocked against endwise movement in either direction.

in order to provide symmetry to the assembled pieces and member against which the bracket 15 may bear to prevent rotation of the holding member on the bolt 61, complementary blocks 90, 90a extend from a respective side portion, intermediate portion and barrier.

Holes 97, 97a are provided through the intermediate members for passing the bolt 61 threaded in the bracket 15.

It is thus seen from the foregoing description that an arc quenching device is provided that is formed in either one or two pieces to form a unitary member to support permanent magnets providing the quenching flux. The unitary holding member is easily mounted on the contactor or relay by means of a bracket and two threaded bolts. Also, the holding member is small with relatively thin side portions to fit between the pairs of contacts.

The permanent magnets provide a flux that is independent of the current through the contact. Thus the full magnetic field is always available independently of the load current and is effective over a wide range of currents.

The holding member may be marked with an indicia such as a plus or minus sign to indicate the polarity of the magnets. Since the assembly is symmetrical it may be mounted to create a force in either of two directions. The assembly may be mounted in one position when the positive lead is connected to the stationary contact, or in the opposite position if the negative lead is connected to the stationary contact.

The versatility and adaptability of the device is apparent from the foregoing description. The improvements made are defined in the claims appended hereto.

I claim:

1. An arc quenching device comprising a first molded piece having a side panel, a fastening panel extending normal to said side panel, a locking block extending from said side panel and spaced from said fastening panel, a second molded piece having a second side panel, a second fastening panel extending normal to said second side panel, a second locking block extending from said second side panel and spaced from said second fastening panel, said first and second fastening panels overlapping to span the space between said side panels and overlap with a respective locking block, first and second barrier members extending between said panels and in opposite directions from a respective fastening panel to define with said side panels a contact receiving cavity and form an arc barrier between supporting means attached to said fastening panels and first and second magnets in a respective side panel overlapping with a substantial portion of said cavity to provide a flux extending across said cavity to extinguish an are created across separating current carrying contacts positioned in said cavity.

2. A permanent magnet holding member for an arc quenching device comprising spaced side portions extending parallel to one another, an intermediate portion between said side portions having a web normal to said side portions and narrower than the width of said side portions to form notches between said side portions on opposite sides of said web and said intermediate portion having a barrier extending from one side portion to the other and defining a cavity with said side portions for receiving making and breaking contacts, each of said side portions having a recess adapted to receive a permanent magnet and overlapping with a substantial part of said cavity to create in said cavity a flux generally normal to said side portions to extinguish an are formed by current carrying contacts breaking in a movement generally parallel to said side portions.

3. In combination with an electric contactor having a pair of make and break current carrying contacts, an arc quenching means attached to the contactor by a supporting bracket, said arc quenching means having two spaced side portions and an intermediate portion between said side portions, said side portions having inwardly facing walls to form with said intermediate portion an open ended contact receiving cavity and having outwardly facing walls with permanent magnets on opposite sides of said side portions from said cavity in an overlapping relation to provide a flux through said cavity normal to the relative movement of said contacts for extinguishing an are formed on separation of said contacts, and supporting means located on the other side of said intermediate portion from said cavity and between said side portions, said supporting means having opposite mounting means for fastening the arc quenching means in one of two positions to relate the flux of the magnets with the polarity on contacts located within said cavity and for interlocking said supporting bracket and said are quenching means in a non-rotative relation.

4. A permanent magnet holding member as set forth in claim 2 wherein said intermediate portion has means for attaching said magnet holding member to a bracket in either of said notches to orientate the flux in relation to the polarity of said contacts.

5. A permanent magnet holding member as set forth in claim 4 wherein the desired relation of the polarity of the contacts and the direction of the field is indicated.

6. An arc quenching device for mounting on a relay having make and break contacts comprising spaced side portions, a barrier extending from one side portion to the other side portion intermediate the ends of said side portions to form a cavity between said side portions for receiving making and breaking contacts, each of said side portions having a permanent magnet overlapping with a substanital part of said cavity to create a flux across said cavity to extinguish an are formed by current carrying contacts breaking in a movement transverse to the flux, a web extending generally normal to said barrier and said side portions and intermediate the edges of said side portions to form notches on opposite sides of said web for mounting the device by single fastening means with the polarity of the flux in the desired relation with the polarity of the contacts.

Wells Apr. 27, 1954 Immel et a1. Feb. 24, 1959 

1. AN ARC QUENCHING DEVICE COMPRISING A FIRST MOLDED PIECE HAVING A SIDE PANEL, A FASTENING PANEL EXTENDING NORMAL TO SAID SIDE PANEL, A LOCKING BLOCK EXTENDING FROM SAID SIDE PANEL AND SPACED FROM SAID FASTENING PANEL, A SECOND MOLDED PIECE HAVING A SECOND SIDE PANEL, A SECOND FASTENING PANEL EXTENDING NORMAL TO SAID SECOND SIDE PANEL, A SECOND LOCKING BLOCK EXTENDING FROM SAID SECOND SIDE PANEL AND SPACED FROM SAID SECOND FASTENING PANEL, SAID FIRST AND SECOND FASTENING PANELS OVERLAPPING TO SPAN THE SPACE BETWEEN SAID SIDE PANELS AND OVERLAP WITH A RESPECTIVE LOCKING BLOCK, FIRST AND SECOND BARRIER MEMBERS EXTENDING BETWEEN SAID SIDE PANELS AND IN OPPOSITE DIRECTIONS FROM A RESPECTIVE FASTENING PANEL TO DEFINE WITH SAID SIDE PANELS A CONTACT RECEIVING CAVITY AND FORM AN ARC BARRIER BETWEEN SUPPORTING MEANS ATTACHED TO SAID FASTENING PANELS AND FIRST AND SECOND MAGNETS IN A RESPECTIVE SIDE PANEL OVERLAPPING WITH A SUBSTANTIAL PORTION OF SAID CAVITY TO PROVIDE A FLUX EXTENDING ACROSS SAID CAVITY TO EXTINGUISH AN ARC CREATED ACROSS SEPARATING CURRENT CARRYING CONTACTS POSTIONED IN SAID CAVITY. 